By surrounding, with a freezing mixture; a small glass vessel containing water, and a mercury thermometer, the temperature of the water may be reduced to--10deg. C. or--12deg. C. without freezing the water. A slight movement of the thermometer in the water starts the freezing and the temperature quickly rises to 0deg. C. (2.) Place a thermometer in a glass vessel containing water at 30deg. C. and a second thermometer in a large bath of mercury at -10deg. C. Immerse the glass vessel in the mercury. The temperature of the water will gradually fall to 0deg. C., when the water will begin to freeze and its temperature become constant. In the meantime the temperature of the mercury bath rises, and continues to do so while the water is freezing. (3.) Dissolve two weights of Glauber's salt in one weight of hot water, cover the solution with a thin layer of oil and allow to cool, in perfect quiet, to the temperature of the room. By plunging a thermometer into the still liquid substance, solidification (crystallization) is started and the temperature rapidly rises. Dr. Arnott found that this experiment was successful after keeping the solution in the liquid condition for five years. (4.) Mix equal quantities of dilute sulphuric acid and of a saturated solution of calcium chloride (not chloride of lime), the two liquids having been allowed time to acquire the temperature of the room. The two liquids are converted into solid calcium sulphate, with a marked increase of temperature. In this case, as in some of the other cases, part of the heat observed is probably due to chemical action, but more to the conversion of the latent heat of the liquids. (5.) To three weights of quicklime add one weight of water. The water will be completely solidified in the slaking of the lime with remarkable thermal manifestations. Carts containing quick lime have been set on fire by exposure to heavy rains.